These 1 to 3 and 2 to 4 terminology are confusing? I still do not get it that "1" and "2" are referring to edge(s)? And what are "3" and "4"? I cannot visually count 3 and 4 of what? The color chart by member Don Newman did not help either. Please help explain. Thank you.
Yeah basically think about it as what comes before and what comes after. So you have something over here and then you have something else. As Martin's pictures show, you have 3 incoming edges and then they turn into 1 outgoing edge. Then in the other one you have 4 edges and then you only have 2 edges. So it's 3 to 1 and 4 to 2.
It's like alchemy. You have 4 of a certain stuff and you're like man 4 is too much, I can't deal with 4, let me do the alchemy magic and bam, now I have 2, much easier to deal with 2. When you model things in 3D, too much geometry can be hard to control, so it's a way to simplify the mesh to gain more control.
Hi 
spikeyxxx and 
dostovel, Thank you. I think I got it now. Since all the visuals in the lesson, the images as well as the demo file are all about face loops and faces flow pattern. I some how see the faces only (ie your attached left image have two columns of faces to 4 columns and right image have three columns to five columns). It never occurred to me that it was counted this way. (Note: because of my perception on faces flow, the left image was interpreted as 3 edges to 5 edges!😕).
